Lyme Disease — MCQs
A young man, home on leave from the military, went camping in the woods to detect deer movement for future hunting. Ten days later, he developed fever, malaise, and myalgia. Leukopenia and thrombocytopenia were observed, as well as several tick bites. Which of the following statements best describes human monocytic ehrlichiosis (HME)?
Soft tick transmits:
A farmer presents with severe leg pain, fever, chills, retro-orbital pain, and bilateral conjunctival suffusion. What is the most likely diagnosis?
A 25-year-old male university student presented with a history of multiple tick bites 45 days prior, followed by recurring episodes of high-grade fever, headache, myalgias, arthralgias, nausea, and occasional vomiting. Each episode lasted approximately 6-7 days with symptom-free intervals of 9-10 days. Physical examination revealed mild splenomegaly and skin lesions. A Wright stain of the patient's peripheral blood smear was performed. What is the first oral drug of choice for this patient?
Erythema chronicum migrans is associated with which of the following conditions?
Which of the following pairs of conditions is incorrectly matched?
Which of the following is the carrying agent for Lyme disease?
A patient presents with multiple hypopigmented and hypesthetic patches on the lateral aspect of the forearm, with abundant acid-fast bacilli (AFB) and granulomatous inflammation on histology. What is the most likely diagnosis?
Erysipelas is caused by which bacterium?
Which subtype of leprosy has the maximum number of TH1 cells?
Lyme Disease Indian Medical PG Practice Questions and MCQs
Question 1: A young man, home on leave from the military, went camping in the woods to detect deer movement for future hunting. Ten days later, he developed fever, malaise, and myalgia. Leukopenia and thrombocytopenia were observed, as well as several tick bites. Which of the following statements best describes human monocytic ehrlichiosis (HME)?
- A. It is a fatal disease transmitted by the bite of a dog
- B. Clinical diagnosis is based on the presence of erythema migrans (EM)
- C. Diagnosis is usually made serologically but morulae may be seen in the cytoplasm of monocytes (Correct Answer)
- D. Symptoms include vomiting and paralysis
Explanation: Diagnosis is usually made serologically but morulae may be seen in the cytoplasm of monocytes - **Human monocytic ehrlichiosis (HME)** is caused by *Ehrlichia chaffeensis*, an obligate intracellular bacterium that infects monocytes. [1] - The gold standard for diagnosis is often **serology** (e.g., indirect immunofluorescence assay), but microscopic examination of peripheral blood smears may reveal characteristic **morulae** (microcolony of bacteria) within the cytoplasm of monocytes, especially in the early stages of infection. *It is a fatal disease transmitted by the bite of a dog* - HME is typically transmitted by the **lone star tick** (*Amblyomma americanum*), not by dog bites. While severe cases can be fatal, it is not universally fatal and is generally treatable with antibiotics. - The primary vector is the lone star tick, with reservoir hosts including white-tailed deer. [1] *Clinical diagnosis is based on the presence of erythema migrans (EM)* - **Erythema migrans (EM)** is the characteristic rash associated with **Lyme disease**, caused by *Borrelia burgdorferi*, and is not seen in HME. [1] - HME symptoms include fever, headache, malaise, and muscle aches, often accompanied by **leukopenia** and **thrombocytopenia**, but no distinctive rash like EM. *Symptoms include vomiting and paralysis* - While vomiting can occur with HME, **paralysis** is not a typical symptom of this disease. - Symptoms more commonly include **fever, headache, malaise, muscle aches, leukopenia, and thrombocytopenia**.
Question 2: Soft tick transmits:
- A. Tularemia
- B. Indian tick typhus
- C. Relapsing fever (Correct Answer)
- D. KFD
Explanation: ***Relapsing fever*** - **Soft ticks** (Ornithodoros species) are the primary vectors for **tick-borne relapsing fever**, specifically transmitting spirochetes of the genus *Borrelia*. - The disease is characterized by recurrent episodes of **fever**, **headache**, and **fatigue**, alternating with afebrile periods. *Tularemia* - While tularemia can be transmitted by ticks, it is primarily associated with **hard ticks** (e.g., Dermacentor, Amblyomma) and not typically soft ticks. - The causative agent is *Francisella tularensis*, which can also be acquired through contact with infected animals or contaminated water. *Indian tick typhus* - This is a form of spotted fever group rickettsiosis caused by *Rickettsia conorii*, typically transmitted by **hard ticks** like *Rhipicephalus sanguineus*. - It is characterized by fever, rash, and a characteristic **eschar** at the bite site. *KFD* - **Kyasanur Forest Disease (KFD)** is a viral hemorrhagic fever transmitted by **hard ticks**, particularly *Haemaphysalis spinigera*. - It is endemic to India and involves symptoms such as high fever, headache, and hemorrhage.
Question 3: A farmer presents with severe leg pain, fever, chills, retro-orbital pain, and bilateral conjunctival suffusion. What is the most likely diagnosis?
- A. Dengue fever
- B. Leptospirosis (Correct Answer)
- C. Malaria
- D. Rickettsia infection
Explanation: **Leptospirosis** - The combination of **leg pain**, **fever**, chills, **retro-orbital pain**, and **bilateral conjunctival suffusion** (red eyes without frank pus) in a farmer (occupational exposure to contaminated water/soil) is highly suggestive of **leptospirosis** [1]. - **Conjunctival suffusion** is a classic and distinctive sign of leptospirosis, differentiating it from many other febrile illnesses [1]. *Dengue fever* - While dengue fever can present with **fever**, **retro-orbital pain**, and **myalgia**, **conjunctival suffusion** is not a typical feature, and severe leg pain is less emphasized compared to leptospirosis [2]. - Dengue is also common in tropical/subtropical regions but the specific constellation of symptoms points away from it [2]. *Malaria* - Malaria presents with classic **cyclic fevers**, **chills**, and **sweats**, often accompanied by headache and muscle aches, and sometimes hepatosplenomegaly. - **Conjunctival suffusion** and severe leg pain are not characteristic features of uncomplicated malaria [2]. *Rickettsia infection* - Rickettsial infections (e.g., Rocky Mountain spotted fever, scrub typhus) often present with **fever**, **headache**, and a **rash**, which can be maculopapular or petechial [3]. - **Retro-orbital pain** and **conjunctival suffusion** are not typical symptoms, and a distinctive rash is generally a key diagnostic clue for rickettsial diseases [3].
Question 4: A 25-year-old male university student presented with a history of multiple tick bites 45 days prior, followed by recurring episodes of high-grade fever, headache, myalgias, arthralgias, nausea, and occasional vomiting. Each episode lasted approximately 6-7 days with symptom-free intervals of 9-10 days. Physical examination revealed mild splenomegaly and skin lesions. A Wright stain of the patient's peripheral blood smear was performed. What is the first oral drug of choice for this patient?
- A. Doxycycline (Correct Answer)
- B. Amoxicillin
- C. Cefuroxime
- D. Erythromycin
Explanation: ***Doxycycline*** - The patient's presentation is classic for **tick-borne relapsing fever (TBRF)** caused by *Borrelia* species. - The **pathognomonic feature** is the **relapsing pattern**: recurring fever episodes (6-7 days) separated by **afebrile intervals** (9-10 days), which distinguishes TBRF from Lyme disease. - **Wright stain of peripheral blood smear** during febrile episodes typically reveals **spirochetes** (unlike Lyme disease where spirochetes are rarely visible in blood). - **Doxycycline 100 mg twice daily** is the **first-line oral treatment** for TBRF, with excellent activity against *Borrelia* spirochetes. - Also covers potential tick-borne coinfections (Ehrlichia, Anaplasma). *Amoxicillin* - While effective for **Lyme disease**, amoxicillin is **less effective for TBRF** compared to tetracyclines. - Used as an alternative in **pregnant women or children <8 years** when doxycycline is contraindicated. - Does not cover rickettsial coinfections that doxycycline would treat. *Cefuroxime* - This **second-generation cephalosporin** can be used as an alternative for Lyme disease. - However, it is **not the first-line choice** for the relapsing fever pattern seen in this case. - Doxycycline remains superior due to broader coverage and better efficacy for TBRF. *Erythromycin* - **Erythromycin** has **poor efficacy** against *Borrelia* species and is **not recommended** for TBRF or Lyme disease. - Higher relapse rates and treatment failures make it an inappropriate choice. - Modern macrolides (azithromycin) have better activity but still inferior to doxycycline.
Question 5: Erythema chronicum migrans is associated with which of the following conditions?
- A. Lyme disease (Correct Answer)
- B. Glucagonoma
- C. Gastrinoma
- D. Phaeochromocytoma
Explanation: ***Lyme disease*** - **Erythema chronicum migrans** (ECM) is the characteristic expanding annular rash seen in the early localized stage of **Lyme disease**. - It results from infection with **Borrelia burgdorferi**, transmitted by **Ixodes ticks**. *Glucagonoma* - This is a pancreatic neuroendocrine tumor that secretes **glucagon**. - It is classically associated with **necrolytic migratory erythema**, a distinct rash, not erythema chronicum migrans. *Gastrinoma* - A gastrinoma is a tumor that secretes **gastrin**, leading to **Zollinger-Ellison syndrome**, characterized by severe peptic ulcer disease. - It is not associated with skin rashes like erythema chronicum migrans. *Phaeochromocytoma* - This is a tumor of the adrenal medulla that secretes **catecholamines**, causing symptoms like hypertension, palpitations, and headaches. - It does not present with erythema chronicum migrans or other characteristic skin rashes.
Question 6: Which of the following pairs of conditions is incorrectly matched?
- A. Erythema gyratum repens - malignancy
- B. Erythema marginatum - rheumatic fever
- C. Necrotic acral erythema - HCV
- D. Erythema chronicum migrans - malignancy (Correct Answer)
Explanation: ***Erythema chronicum migrans - malignancy*** - **Erythema chronicum migrans** is the characteristic skin lesion of **Lyme disease**, caused by the bacterium *Borrelia burgdorferi*, transmitted by ticks. - It is not associated with malignancy; rather, its presence indicates a **bacterial infection** requiring antibiotic treatment. *Erythema marginatum - rheumatic fever* - **Erythema marginatum** is a **major diagnostic criterion** for **rheumatic fever**, a post-streptococcal inflammatory disease. - The rash is characterized by non-itchy, pink or red macules with raised, serpiginous borders that spread outwards, often transient. *Erythema gyratum repens - malignancy* - **Erythema gyratum repens** is a rare **paraneoplastic dermatosis** strongly associated with various internal malignancies, most commonly lung cancer. - It presents as a characteristic **wood-grain-like pattern** of concentric, migratory erythematous bands. *Necrotic acral erythema - HCV* - **Necrotic acral erythema** is a skin condition that predominantly affects the hands and feet and has a strong association with **hepatitis C virus (HCV) infection**. - It presents with violaceous plaques that can ulcerate and become necrotic, often in patients with chronic HCV.
Question 7: Which of the following is the carrying agent for Lyme disease?
- A. Anopheles
- B. Ixodes scapularis ticks (Correct Answer)
- C. Louse
- D. Rat flea
Explanation: ***Ixodes scapularis ticks*** - *Ixodes scapularis* ticks (deer ticks) are the primary **vectors for Lyme disease** (caused by *Borrelia burgdorferi*) in North America [1]. - In Europe, *Ixodes ricinus* is the main vector for Lyme disease. - Lyme disease presents with characteristic **erythema migrans** rash, followed by potential neurological, cardiac, and arthritic complications [1]. - Lyme arthritis commonly affects large joints, particularly the **knee**, causing inflammatory arthritis [1]. *Anopheles* - **Anopheles mosquitoes** are the primary vectors for **malaria**, not Lyme disease [2]. - Malaria is caused by *Plasmodium* parasites and presents with fever, chills, and hemolytic anemia [2]. *Louse* - **Lice** are vectors for diseases such as **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever** (caused by *Borrelia recurrentis*) [3]. - They are not associated with the transmission of Lyme disease. *Rat flea* - **Rat fleas** (e.g., *Xenopsylla cheopis*) are the primary vectors for **bubonic plague** (caused by *Yersinia pestis*) and **murine typhus**. - These insects do not transmit Lyme disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 389-390. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 400. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 392-393.
Question 8: A patient presents with multiple hypopigmented and hypesthetic patches on the lateral aspect of the forearm, with abundant acid-fast bacilli (AFB) and granulomatous inflammation on histology. What is the most likely diagnosis?
- A. Tuberculoid leprosy
- B. Intermediate leprosy
- C. Borderline leprosy (Correct Answer)
- D. Lepromatous leprosy
Explanation: ### Explanation The correct answer is **Borderline leprosy (C)**. #### 1. Why Borderline Leprosy is Correct The diagnosis of leprosy is based on the Ridley-Jopling classification, which correlates clinical features with the host's immune response. * **Clinical Presentation:** The presence of multiple hypopigmented and **hypesthetic** (reduced sensation) patches is characteristic of the borderline spectrum. * **Histopathology:** The mention of **abundant acid-fast bacilli (AFB)** alongside **granulomatous inflammation** is the key differentiator. In the borderline spectrum (specifically Borderline Lepromatous - BL), the cell-mediated immunity is low enough to allow significant bacillary multiplication (high Bacterial Index), yet high enough to still form organized granulomas. #### 2. Why Other Options are Incorrect * **A. Tuberculoid leprosy (TT):** Characterized by high immunity. Clinically, there are very few lesions (1-3) with complete anesthesia. Histologically, granulomas are well-formed, but **AFB are absent** (paucibacillary). * **B. Intermediate leprosy:** This is an early, transitory stage. It usually presents as a single, ill-defined macule with vague sensory loss. It does not show abundant AFB or well-developed granulomatous inflammation. * **D. Lepromatous leprosy (LL):** Characterized by negligible immunity. While AFB are extremely abundant (globi), the histology shows **diffuse histiocytic infiltration** (Virchow cells/foam cells) rather than organized granulomatous inflammation. #### 3. NEET-PG High-Yield Pearls * **Pathognomonic sign:** Asymmetrical nerve enlargement is typical of Borderline Leprosy. * **Bacterial Index (BI):** TT (0), BT (0-1+), BB (3-4+), BL (4-5+), LL (5-6+). * **Lepromin Test:** Strongly positive in TT, negative in LL. It measures delayed-type hypersensitivity (prognostic, not diagnostic). * **Treatment:** WHO MDT for Multibacillary (MB) leprosy (including Borderline and LL) lasts 12 months, whereas Paucibacillary (PB) lasts 6 months.
Question 9: Erysipelas is caused by which bacterium?
- A. Staphylococcus aureus
- B. Staphylococcus albus
- C. Streptococcus pyogenes (Correct Answer)
- D. Haemophilus
Explanation: ### Explanation **Correct Answer: C. Streptococcus pyogenes** **Medical Concept:** Erysipelas is a distinct clinical variant of superficial cellulitis. It is primarily caused by **Group A Beta-hemolytic Streptococci (GABHS)**, most commonly ***Streptococcus pyogenes***. The infection involves the upper dermis and superficial lymphatics. Characteristically, it presents as a well-demarcated, fiery-red, edematous, and tender plaque. The "sharp borders" are a hallmark feature because the infection is superficial, allowing for a clear distinction between involved and uninvolved skin. **Analysis of Incorrect Options:** * **A. *Staphylococcus aureus*:** While *S. aureus* is the most common cause of **Cellulitis** (which involves the deeper dermis and subcutaneous fat), it is rarely the primary cause of classic Erysipelas. *S. aureus* is more associated with purulent infections like furuncles and abscesses. * **B. *Staphylococcus albus*:** Now known as *Staphylococcus epidermidis*, this is a commensal organism of the skin flora and is generally non-pathogenic unless it involves prosthetic implants or biofilms. * **C. *Haemophilus*:** *Haemophilus influenzae* was historically a common cause of facial cellulitis in children, but its incidence has significantly decreased due to the Hib vaccine. It does not typically cause the classic clinical picture of erysipelas. **High-Yield Clinical Pearls for NEET-PG:** * **Milian’s Ear Sign:** Erysipelas can involve the pinna (ear) because the skin is tightly adherent to the cartilage with no subcutaneous fat. Cellulitis cannot involve the pinna. * **Clinical Distinction:** Unlike cellulitis, erysipelas has **raised, sharply defined borders**. * **Common Site:** The lower limbs are the most frequent site, followed by the face (butterfly distribution). * **Treatment of Choice:** Penicillin is the first-line treatment for *Streptococcus pyogenes*.
Question 10: Which subtype of leprosy has the maximum number of TH1 cells?
- A. Tuberculoid (TT) (Correct Answer)
- B. Bande (BB)
- C. Lepromatous (LL)
- D. Borderline leprosy
Explanation: In leprosy, the clinical presentation is determined by the host's **Cell-Mediated Immunity (CMI)** against *Mycobacterium leprae*. This response is governed by the balance between **Th1** and **Th2** helper T-cells. ### Why Tuberculoid (TT) is Correct: **Tuberculoid Leprosy (TT)** represents the high-resistance end of the Ridley-Jopling spectrum. In these patients, the body mounts a vigorous **Th1-mediated immune response**. Th1 cells secrete pro-inflammatory cytokines like **IL-2 and IFN-γ**, which activate macrophages to kill the bacilli. Because the Th1 response is at its peak, the bacterial load is very low (paucibacillary), and the Mitsuda skin test is strongly positive. ### Why the Other Options are Incorrect: * **Lepromatous (LL):** This is the opposite end of the spectrum. Here, the immune response is dominated by **Th2 cells**, which secrete cytokines like **IL-4, IL-5, and IL-10**. This suppresses CMI and promotes antibody production, which is ineffective against intracellular *M. leprae*, leading to high bacterial loads (multibacillary). * **Borderline (BB) and Borderline Leprosy:** These represent the immunologically unstable middle of the spectrum. They have a mixture of Th1 and Th2 responses but never reach the maximal Th1 levels seen in polar Tuberculoid leprosy. ### High-Yield Clinical Pearls for NEET-PG: * **Th1 Response (TT):** High CMI, low bacilli, positive Lepromin test, cytokines: **IL-2, IFN-γ, IL-12**. * **Th2 Response (LL):** Low CMI, high bacilli, negative Lepromin test, cytokines: **IL-4, IL-5, IL-10**. * **Histology:** TT shows well-formed granulomas with epithelioid cells and many lymphocytes; LL shows "foamy macrophages" (Virchow cells) packed with bacilli (globi). * **Mnemonic:** **T**uberculoid = **T**h1 = **T**ight (strong) immunity.
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